Field of the Invention
“Gas filled” Light Emitting Diodes systems or “Gas filled” LED bulbs are proposed as incandescent-replacement lamps and in some cases also as High Intensity Discharge (HID) replacement lamps; these LED bulbs typically consist of LEDs based structures (for example the so called “LED filaments” based on a series of tiny LEDs arranged on narrow and long substrates or LEDs mounted, for example by soldering, on boards) sealed inside glass bulbs filled with a filling gas having high thermal conductivity so that the presence of a specific heat sink is not necessary. More information on this type of lamps can be found in the European patent Nr. EP2535640.
Description of the Related Art Including Information Disclosed under 37 CFR 1.97 and 1.98
The usually adopted gas is the highly thermally conductive helium or filling mixtures with a high concentration of He, and the filling pressure may range from 100 mbar to 1200 mbar, in such a way that during operation LEDs can work at temperatures lower than the critical values (typically it is suggested that the operating temperature is below 125° C. in order to prevent accelerated degradation mechanisms and to avoid an appreciable reduction of the luminous efficacy).
Even though Helium is actually the most diffused gas, also hydrogen has been described as suitable gas, for example in the US patent application 2004/201990. Hydrogen presents some technical advantages in view of its higher thermal conductivity with respect to helium, in addition its lower viscosity makes the convective mechanisms more effective in thermal dissipation and furthermore its lower fugacity reduces the gas loss during the long lamp lifetime but its use creates also a major drawback linked to safety reasons.